I agree that Redis can be an architectural smell. You can shoehorn it in where it doesn't belong.
It's easy to work with and does it's job so well that for a certain type of dev it's easier to implement caching than understand enough SQL to add proper indices.
Its funny, because once you go through the effort of determining which query fields you should compose to make your cache key, you're 95% of the way to the index you should have had in the first place.
It's easy to work with and does it's job so well that for a certain type of dev it's easier to implement caching than understand enough SQL to add proper indices.